The following note is being added to the README of 144500-19 to warn customers about this issue:

"Do not install this patch on systems running EMC PowerPath, as all currently
released EMC PowerPath versions (as of August 18th 2011) are incompatible with
this patch.
EMC PowerPath is using a private Solaris structure which was modified in this
patch to fix a race condition. Applications should not use private Solaris
interfaces as they are subject to change.
EMC PowerPath Engineering is working on a 5.3 patch release to resolve this
issue and have published ETA emc275344 on https://powerlink.emc.com, which
contains further information."

Oracle are making every effort to assist EMC in getting a fix to customers for this issue and in the meantime ensuring that everything possible is being done to ensure that susceptible customers do not unwittingly hit this issue.

In addition, the current "NOTE 9" is being completely removed from the README of 144500-19, to avoid any further confusion:

NOTE 9: This patch causes a minor issue with systems using EMCPowerPath,
as explained below:

On changing the label of a EMC PowerPath pseudo disk from EFI to SMI,
the pseudo disk with a new SMI label may not have the :h device node
created.

Today is the target date for the release of the EMC patch. I can't find any notifications but looks as though I will need to register for support updates with EMC. Anyone have any information on this patch?

I confirm that the updated version of PowerPath (5.3.P02_b001) which EMC has released on time (Oct 7, 2011) solves the problem. After updating to that PowerPath release we managed to successfully update Solaris kernel to 144500-19 and subsequently to 147440-03. (Including upgrade to Solaris 10 Update 10 worked fine too).